Fried oysters, or kaki furai, as they are called, are a Japanese restaurant staple. They are the plumper and juicier cousins of New England’s fried clams — savory breaded and deep-fried morsels that cry out for a cold beer. They’re often accompanied by thinly sliced cabbage, but the perfectly fried Hama Hama oysters at R23 arrive alongside a segmented melon slice, a scoop of potato salad and a wedge of lemon. The traditional soy and ketchup-based dipping sauce is augmented with a smear of hot mustard. It’s a humble dish elevated by the elegant art and design of this warehouse district restaurant, not to mention R23’s refined appetizers, salads and sushi. If all this isn’t enough to put a smile on your face, the Frank Gehry-designed cardboard chairs and beautiful restrooms might do the trick.